FACTS-based Schemes for Distribution Networks with Dispersed Renewable Wind Energy

1
FACTS-based Schemes for Distribution Networks
with Dispersed Renewable Wind Energy

• Professor Dr. Adel M Sharaf
• ECE Dept., UNB
• Fredericton, NB, Canada

2
Outline

• Introduction
• Motivations
• Sample Study System Modelling
• Novel FACTS-based Schemes
• Controller Tuning
• Digital Simulation
• Conclusions and Recommendations

3
Introduction

• Wind is a renewable Green Energy source

Load
kinetic Energy
Mechanical Energy
Electrical Energy
4
Introduction

• Wind is also a clean Abundant Source
• No Emissions, No Pollutions

carbon dioxide
sulfur dioxide
particulates
5
Introduction

• Wind energy is a promising green energy and
  becomes increasingly viable popular.
• The cost of wind-generated electric energy has
  dropped substantially(6-7 per KWH).
• By 2005, the worldwide capacity had been
  increased to 58,982 MW-Cost is 2000-2500/KW
• World Wind Energy Association expects 120,000 MW
  to be installed globally by 2010.

6
Introduction
Total installed wind power MW-capacity (data from
World Wind Energy Association)

7
Introduction

• Wind Energy Conversion System (WECS) Using Large
  Squirrel Cage/Slip ring Induction Generators
• Stand alone-Village Electricity
• Electric Grid Connected WECS
• Distributed/Dispersed/Farm Renewable Wind Energy
  Schemes
• Located closer to Load Centers
• Low Reliability, Utilization, Security

8
Motivations

• Energy crisis
• Shortage of conventional fossil fuel based energy
  
• Escalating/rising cost of fossil fuels
• Environmental/Pollution/GHG Issues
• Greenhouse gas emission /Carbon Print
• Acid Rain/Smog/VOC-Micro-Particulates
• Water/Air/Soil Pollution Health Hazards

9
Motivations

• Large wind farm utilization is also emerging
  (50MW-250 MW) Sized Using Super Wind driven
  Turbines 1.6, 3.6, 5 MW Sizes
• Many new interface Regulations/Standards/PQ
  Requirements regarding full integration of large
  distributed/dispersed Wind Farms into Utility
  Grid.

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Motivations

• Challenges for Utility GridWind Integration.
• Stochastically-Highly Variable wind power
  injected into the Utility Grid.
• Increased Wind MW-Power penetration Level.
• Low SCR-Weak Distribution/Sub Transmission/Transmi
  ssion Networks
• - Mostly of a Radial Configuration
• - Large R/X ratio distribution Feeder with high
  Power Losses (4-10 ), Voltage Regulation
  Problems/Power Quality/Interference Issues.
• Required Reactive Power Compensation Increased
  Burden brought by the induction generator

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Sample Distribution Study System
L.L.1
L.L.2
N.L.L
T3
T2
T1
L.L.3
Infinite Bus
WECS
I.M.
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WECS-Decoupled Interface Scheme
Uncontrolled Rectifier
PWM Inverter
I.G.
Lf
To Grid
Cf
DC Link Interface
Wind Turbine
Cself
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System Description-wind turbine

• Wind turbine model based on the steady-state
  power characteristics of the turbine
• S -- the Total BladeArea swept by the rotor
  blades (m2)
• v -- the wind velocity (m/s)
• ?--air density (kg/v3)

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System Description
tip speed ratio ? is the quotient between the
tangential speed of the rotor blade tips and the
undisturbed wind velocity
C10.5176, C2116, C30.4, C45, C521 and
C60.0068
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System Description Wind speed

• The dynamic wind speed model consists of four
  basic components
• Mean wind speed-14 m/s
• Wind speed ramp with a slope of 5.6
• Wind gust
• Ag the amplitude of the gust
• Tsg the starting time of the gust
• Teg the end time of the gust
• Dg Teg - Tsg
• Turbulence components a random Gaussian series

16
Wind Speed Dynamic Model
The eventual wind speed applied to the wind
turbine is the summation of all four key
components.
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MPFC-FACTS Scheme 1

• Complementary PWM pulses to ensure dynamic
  topology change between switched capacitor and
  tuned arm power filter
• Two IGBT solid state switches control the
  operation of the MPFC via a six-pulse diode
  bridge

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Tri-loop Error Driven Controller
Modulation Index
Voltage Stabilization loop
Current Harmonic Tracking Loop
Current Dynamic Error Tracking loop
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DVR-FACTS Scheme 2
If S1 is high and S2 is low, both the series and
shunt capacitors are connected into the circuit,
while the resistor and inductor will be fully
shorted

• A combination of series capacitor and shunt
  capacitor compensation
• Flexible structure modulated by a Tri-loop Error
  Driven Controller

If S1 is low and S2 is high, the series capacitor
will be removed from the system, the resistor and
inductor will be connected to the shunt
capacitors as a tuned arm filter
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HPFC-FACTS Scheme 3

• Use of a 6-pulse VSC based APF to have faster
  controllability and enhanced dynamic performance
• Combination of tuned passive power filter and
  active power filter to reduce cost

Coupling capacitor
Coupling transformer
PWM converter
Passive Filter tuned near 3rd harmonic frequency
DC Capacitor to provide the energizing voltage
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Novel Scheme-3 Multi-loop Error Driven Controller
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Novel Decoupled Multi-loop Error Driven Controller

• Using decoupled direct and quad. (d , q) voltage
  components
• Using The Phase Locked Loop (PLL) to get the
  required synchronizing signal- phase angle of the
  synthesized VSC-Three Phase AC output voltages
  with Utility-Bus
• Using Proportional plus Integral (PI) controller
  to regulate any tracked errors
• Using Pulse Width Modulation-PWM with a variable
  modulation index -m

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Novel Decoupled Multi-loop Error Driven Controller

• Outer-Voltage Regulator Tri-loop Dynamic
  Error-Driven controller
• The voltage stabilization loop
• The current dynamic error tracking loop
• The dynamic power tracking loop
• Inner-Voltage Regulator Mainly to control the
  DC-Side capacitor charging and discharging
  voltage to ensure almost a near constant DC
  capacitor voltage

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Controller Tuning

• Control Parameter Selection/optimization
• Using a guided Off-Line Trial-and-Error Method
  based on successive digital simulations
• Minimize the objective function-Jo
• Find optimal Gains kp, ki and individual loop
  weightings (?) to yield a near minimum Jo under
  different set-selections of the controller
  parameters

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Digital Simulation

• Digital Study System Validation is done by using
  Matlab/Simulink/Sim-Power Software Environment
  under a sequence of excursions
• Load switching/Excusrions
• At t 0.2 second, the induction motor was
  removed from bus 5 for a duration of 0.1 seconds
• At t 0.4 second, linear load was removed from
  bus 4 for a duration of 0.1 seconds
• At t 0.5 second, the AC distribution system
  recovered to its initial state.
• Wind-Speed Gusting changes modeled by dynamic
  wind speed-Software model

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Digital Simulation

• Digital Simulation Environment
• MATLAB /Simulink/Sim-Power
• Using the discrete simulation mode with a sample
  time of 0.1 milliseconds
• The digital simulations were carried out without
  and with the novel FACTS-based devices located at
  Bus 5 for 0.8 seconds

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System Dynamic Responses at Bus 2 without and
with MPFC
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System Dynamic Responses at Bus 3 without and
with MPFC
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System Dynamic Responses at Bus 5 without and
with MPFC
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The frequency variation at the WECS interface
without and with MPFC
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System Dynamic Responses at Bus 2 without and
with DVR
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System Dynamic Responses at Bus 3 without and
with DVR
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System Dynamic Responses at Bus 5 without and
with DVR
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The frequency variation at the WECS interface
without and with DVR
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System Dynamic Responses at Bus 2 without and
with HPFC
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System Dynamic Responses at Bus 3 without and
with HPFC
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System Dynamic Responses at Bus 5 without and
with HPFC
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The frequency variation at the WECS interface
without and with HPFC
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Comparison of Voltage THD with Different
Compensation Scheme
Bus number Without compensator With MPFC With DVR With HPFC
1 28.39 4.90 11.9 4.99
2 32.70 4.60 12.2 4.88
3 35.95 4.29 12.6 4.69
4 35.75 3.51 12.2 4.51
5 35.77 3.32 13.1 3.90
6 36.04 3.57 8.57 4.57
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Comparison of Steady-state Bus Voltage with
Different Compensation Scheme
Bus number Without compensator With MPFC With DVR With HPFC
1 0.97 1.02 1.01 1.05
2 0.95 1.00 1.03 1.05
3 0.94 1.00 1.02 1.05
4 0.89 0.99 1.02 1.05
5 0.86 0.99 1.02 1.06
6 0.83 0.96 1.03 1.05
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Conclusions

• Three Novel FACTS-based Converter Control
  schemes, namely the MPFC, the DVR, and the HPFC,
  have been Developed and validated for voltage
  stabilization, power factor correction and power
  quality improvement in the distribution network
  with dispersed wind energy integrated.

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Recommendation

• The Low-Cost MPFC-Scheme 1 is preferred for low
  to medium size wind energy integration schemes
  (from 600 to 5000 kW).
• The DVR-Scheme 2 is good for Strong AC
  sub-transmission and distribution systems with
  large X/R ratio
• The HPFC-Scheme 2 Active Power Filter Capacitor
  Compensator is most suitable for Larger
  Wind-Farms with MW-energy penetration level (100
  MW or above).

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Recommendation

• The schemes validated in this research need to be
  fully tested in the distribution network with
  real dispersed wind energy systems.
• This research can be extended to the grid
  integration of other dispersed renewable energy.
• Other Artificial Intelligence based control
  strategies can be investigated in future work.

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Conclusions

• A Validation Study of a unified sample study
  system Using the ATLAB/Simulink
• A dynamic wind speed software model was developed
  to simulate the varying Random/Stochastic and
  temporal wind variations in the MATLAB/Simulink
• Three Novel FACTS based Stabilization Schemes
  were validated using digital simulations
• Novel Control strategies using dynamic
  Multi-Loop Decoupled Controllers were developed
  Validated

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Publications

• 1 A. M. Sharaf and Weihua Wang, A Low-cost
  Voltage Stabilization and Power Quality
  Enhancement Scheme for a Small Renewable Wind
  Energy Scheme, 2006 IEEE International Symposium
  on Industrial Electronics, 2006, p.1949-53,
  Montreal, Canada
• 2 A. M. Sharaf and Weihua Wang, A Novel
  Voltage Stabilization Scheme for Standalone Wind
  Energy Using A Dynamic Sliding Mode Controller,
  Proceeding- the 2nd International Green Energy
  Conference, 2006, Vol. 2, p.205-301, Oshawa,
  Canada
• 3 A. M. Sharaf, Weihua Wang, and I. H. Altas,
  Novel STATCOM Controller for Reactive Power
  Compensation in Distribution Networks with
  Dispersed Renewable Wind Energy, 2007 Canadian
  Conference on Electrical and Computer
  Engineering, Vancouver, Canada, April, 2007
• 4 A. M. Sharaf, Weihua Wang, and I. H. Altas,
  A Novel Modulated Power Filter Compensator for
  Renewable Dispersed Wind Energy Interface, the
  International Conference on Clean Electrical
  Power, 2007, Capri, Italy, May, 2007
• 5 A. M. Sharaf, Weihua Wang, and I. H. Altas,
  A Novel Modulated Power Filter Compensator for
  Distribution Networks with Distributed Wind
  Energy (Accepted by International Journal of
  Emerging Electric Power System)

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THANK YOU
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